Reroute the return line??

enkeivette

enkeivette

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Mar 30, 2008
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Got the last piece of the puzzle for my powerplant, a Holley Ultra HP fuel pump... after this I can work on guiding my missle. :)

So, this pump is serious business, rated at 200 gph. And it's setup for a 5/8" inlet. :twitch: I'm not going to go that crazy, but I was thinking about rerouting the return line to work in tandem with the supply line... since this pump doesn't require a return line. The supply line in conjunction with the return line would be the equivalent of about a 1/2" line, which should be fine.

So, what do I have to do at the tank to setup the return line for suck??? Other than using the Shwartz...

Suck suck suck!!!
megamaid-spaceballs.jpg
 
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I read here/somewhere that the stock 3/8 line was good for 5-600 hp....so why bother??

:goodnight:
 
I made a calculated 520 at the engine with 5lbs of boost (assuming 17% loss), mathematically I should have 720 now with the 13lbs I am making. Not including the ported intake, bigger ratio (1.65) rockers, better air to fuel ratio (14.5 down to 12:1), and intercooler. So 700 at the engine would be a safe estimate. It's enough to suck my 130gph pump dry by 3rd gear.

Obviously I don't want to pump the fuel in circles, I want to know how I can extend the return so that it can suck. Or maybe drop a 1/2" line in the tank, and Y it off to the feed and return lines. (Which is what I will do at the pump.)

I just have no idea how people install custom fuel lines in the first place, looking for some instruction.
 
enkeivette said:
I made a calculated 520 at the engine with 5lbs of boost (assuming 17% loss), mathematically I should have 720 now with the 13lbs I am making. Not including the ported intake, bigger ratio (1.65) rockers, better air to fuel ratio (14.5 down to 12:1), and intercooler. So 700 at the engine would be a safe estimate. It's enough to suck my 130gph pump dry by 3rd gear.

Obviously I don't want to pump the fuel in circles, I want to know how I can extend the return so that it can suck. Or maybe drop a 1/2" line in the tank, and Y it off to the feed and return lines. (Which is what I will do at the pump.)

I just have no idea how people install custom fuel lines in the first place, looking for some instruction.
Click to expand...

Sorry Adam. I misunderstood. Someone else would be better suited to answer.
 
I'm guessing the return doesn't have a screening sock or pickup tube, so you'd suck air. The overall resistance to flow is the area with a length factor or something close to that so you could use an adapter at the pickup and run a 1/2" line and that would have less resistance to flow than a 3/8 the whole length of the car, even though the pickup is 3/8.

I wouldn't do 5/8. That's heater hose size. In a wreck its just going to feed the fire faster.

combined area of 3/8 and 1/4
pi*(.25/2)^^2 = 0.049
pi*(.375/2)^^2=0.110
total = 0.159
.159/.110 = 1.44 44% increase by adding the 1/4 line

area of 5/8
pi*(.625/2)^^2 = 0.307
.307/.11 = 2.8 180% increase over 3/8

area of 1/2
pi*(.5/2)^^2 = 0.196
.196/.11 = 1.78 78% increase over 3/8

On second thought, i think you're on the right track. It would probably be easer to add a pickup tube to the 1/4 than running a new line the length of the car.
 
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That inlet is a -10 AN (I googled that pump), good size but not overkill. Instead of fiddling around trying to add more area to an existing line, why not mount a good electric pump at the rear and force feed the mechanical pump all it wants. No need to add any pressure, just volume.

And to stick with your original question, you'll need to add a line to the bottom of the tank from where the return line enters. The return line fitting on the tank is just a nipple to put a hose on. It's at the top of the tank.
 
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If you haven't bought the pump yet, or even if you have and might return it, take a look at these pumps. Designed and made by Howard Stewart of the Stewart water pump fame (sold out years ago)
At any point, his site has many pages of useful info and schematics on pumps, systems and regulators.

As far as plumbing, I would do it right. You can get thin wall hydraulic tubing at any decent hydraulic or steel supply and use an Imperial bender (only does one size in the bigger sizes). You can do it in pieces (easier) and use AN or JIC flare unions to join if necessary. No pickup sock needed, just use an inline flared suction screen. Only really tricky tight part is around the rear kickup to the tank. You can do all the pickup install and mods on the removeable sending unit of your tank.

Stewart says a return line isn't necessary and calls his an idle bleed line, but I have always liked to use them for almost any application.
Something else to consider is that Holley recommends rebuilding the pump every 50 hrs, Stewart doesn't.

http://www.racepumps.com/CircleTrackIndex.html

http://www.racepumps.com/Applications-CircleTrack.html

http://www.racepumps.com/Instructions-CircleTrack.html
 
I got a steal on this pump, I'm sticking with it. And I refuse to go electric.


Thank you TimAT, that was the answer I was looking for. Sorry everyone else if what I said was confusing.

Tim, do you know if I can simply pull the return line out, and drop in a longer line, and connect it up? Or is the return line welded into the tank or something??
 
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you can see the return line as well as the supply line on top of the tank thru the hole once you remove the gas lid. you'll see there's rubber hose between the nipple at the tank and the lines. the lines run on top of the frame behind the rear wheel, make sure there's no rust.... my lines crumbled as soon as I touched them....

play it safe and run a new line.... how about SS braided hose?? easy install.....
 
Basically the return is just a short tube with a bell on the outside end of it for a hose and clamp. It "might" be thru the tank 1/4", but I suspect it's closer to flush than that. Won't be enough to put an extension on. It'd be a pull the tank, have it flushed and weld a tube in thing.
 
Karsten, it's a Cali car, rust free. I already replaced the rubber lines back there and the tubes were fine.

Tim, I could do that, is there a screen on the end of the 3/8 line or something? Or can I just drop the new line in down towards the bottom of the tank??
 
enkeivette said:
I got a steal on this pump, I'm sticking with it. And I refuse to go electric.

Tim, do you know if I can simply pull the return line out, and drop in a longer line, and connect it up? Or is the return line welded into the tank or something??
Click to expand...

Mechanical pumps on the engine have some (in my opinion) serious problems. First of all they suck..(using the word in a traditional meaning). Fuel flows up to the mechanical pump inlet due to gravity. The fuel pump diaphragm creates a negative pressure and air pressure and gravity causes a fuel flow from the tank. Of course the long fuel line has bends in it so there's a restriction for fuel flow. Now lets assume that you're getting a 0.5 g acceleration with the car. This acceleration inhibits fuel flow forward to the engine. 0.5 g acceleration is equivalent to having the nose of the car 45 degrees up in the air. Gravity feed of adequate gasoline flow to your engine probably just isn't going to happen.

Are you going to use a supercharger on your engine? You mentioned pounds of boost. Gravity flow of gasoline to the engine fuel pump, acceleration inhibiting gravity flow, and the need to have fuel pump pressure overcome supercharger pressure? Refer to the next sentence below.

You need an electric fuel pump in the tail of the car to pump high pressure gasoline forward to the engine. A regulator up front will drop pressure to that required by a carb. Why don't you accept an electric fuel pump? They are noisy, but the noise is lessened if you use an electric pump speed controller. At low engine rpm, the speed controller operates the fuel pump at a lower rpm so it doesn't make all that awful noise.

The return fuel lines dumps into the top of tank. You can use it for a parallel tank line if you plumb it up. With enough fuel pump pressure from a electric fuel pump in the rear, I'd think a 3/8 inch line would work fine.

For my plumbing in the back, I used cunifer tubing. Its a copper nickel iron alloy, hence Cu (copper), Ni (nickel), Fe(iron). It's been used in production cars, Volvo that I know of. It doesn't rust. It's not as soft as copper and a little softer than steel. It double flares really nicely with hand tools. Google will give the US distributor. On top of the engine I used aluminum tubing. My gas lines are stainless steel from In-Line tubing. I had then install AN fittings at the ends of the lines so I won't have to use rubber hoses and band clamps to connect up the the lines. Remember to put a shut off valve back at the tank outlet. You can work on your gas lines much more conveniently.
 
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68/70Vette, very interesting information, I'd not heard of a speed controller for electric fuel pumps. Can you find those at the usual suspects or are they specialty items?

enkievette, I have a similar, issue, if I hold 2000-2500 rpm in first gear then go WOT, bringing the revs up to about 5500 or closer to 6000, I'm outta gas before the top of third. I'm running a BB calculated to be over 500hp with a Qjet, Edlebrock 140gph mechanicle pump and 3/8 line. I was told going to 1/2 line from the pump to the carb would give me the necessary capacity to get through the issue. Might be worth a try before replumbing everything or adding the electric pump? I would, but I have the front end off the car now....
 
enkeivette said:
Tim, I could do that, is there a screen on the end of the 3/8 line or something? Or can I just drop the new line in down towards the bottom of the tank??
Click to expand...

There is (or was) a sock on the end of the original fuel pickup tube. Think of it as a "pre-filter". I've seen them plugged, mashed closed, and gone.
I think one of the ideas of using it was not only as a filter, but also using it to prevent the fuel pump from sucking a"hole" in the fuel. Cavitation. That's why the oil pickups are not just a straight tube into the oil pan.
 
TimAT said:
enkeivette said:
Tim, I could do that, is there a screen on the end of the 3/8 line or something? Or can I just drop the new line in down towards the bottom of the tank??
Click to expand...

There is (or was) a sock on the end of the original fuel pickup tube. Think of it as a "pre-filter". I've seen them plugged, mashed closed, and gone.
I think one of the ideas of using it was not only as a filter, but also using it to prevent the fuel pump from sucking a"hole" in the fuel. Cavitation. That's why the oil pickups are not just a straight tube into the oil pan.
Click to expand...

:eek:

never knew that, interesting....:twitch:
 
Damoroso

The speed controller is made by Aeromotive. Google Aeromotive fuel pump.
The speed controller supplies chopped 12 volts DC to the fuel pump at idle so the pump runs slow. As engine rpm goes up, the chopped, or 0 vDC, portion of the chopped wave starts to decrease to drive pump rpm up. At about 2500 engine rpm, the speed controller supplies full 12 vDC to the pump. Another nice feature of the controller is that when you turn off the engine, it powers the pump for about 2 seconds and then turns off the pump. No need to put in an oil pressure switch for a safety turn off of the electric pump. My speed controller gets it's engine speed signal from electric tach output by the HEI distributor. The controller will also work with breaker points. The controller has an adjustment to allow you to select the engine rpm when you want the controller to apply full DC voltage to the pump. It also has an override switch, so if the controller fails, you just switch it out of the circuit and apply full continuous 12 DC to the pump.

TimAT

I got rid of the little fiberglass sock on the inside of the fuel tank. On my 68, it looked like it had collapsed and looked pretty restrictive. I have an Aeromotive fuel filter. It's a big canister located right after the fuel pump. I also removed the little porous bronze filters in the carb. I think that big canister will give all the filtering I need.......I think if you want to maximize fuel flow, the porous bronze carb filters need a toss.
............................

I removed the rear sway bar from my 68 and instead have an aluminum bracket attached to the frame...it spans from one side of the frame to the other. The bracket has a L cross section. That's were I mounted my fuel pump and filter. Removing the rear sway bar probably builds a little understear into the car. That's fine with me, I don't want any hint of oversteer for highway driving and changing lanes...no off throttle oversteer for me.
 
68/70 vette, you win electric pumps are better... Actually there was never an argument. But for all the same reasons as I had before, (cost/ already taxed electrical system/ ease of intall) I'm sticking with mechanical. Especially now that the pump is sitting in my bedroom.

And ya, knew about aeromotive speed controllers. My buddy runs one on his turbo 1st gen mustang with a a1000. That's a nice way to bring the cost of the pump up to nearly a grand.
 
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